Comparison of Two Different Volumes of Ropivacaine Used in Nerve Stimulator Guided Inter-scalene Block for Arthroscopic Shoulder Surgery - A Randomized Controlled Trial

Background: This study was conducted to compare the analgesic efficacy of 10 ml versus 20 mL of 0.5% ropivacaine in nerve stimulator guided interscalene brachial plexus block, in patients undergoing arthroscopic shoulder surgery.

Methods: A total of 70 American Society of Anesthesiologists physical status classes 1 and 2 patients, aged 18-65 years, undergoing unilateral arthroscopic shoulder surgery, were randomized into two groups. Group A received single shot inter-scalene block with 20 mL of 0.5% ropivacaine whereas Group B received the same with 10 mL. The primary outcome was difference in the total postoperative fentanyl consumption over 24 h. Secondary outcomes were difference in block onset, intra-operative hemodynamic parameters, intra-operative fentanyl consumption, duration of effective analgesia, visual analogue scale (VAS) scores at various time intervals, duration of motor block, and incidence of hemidiaphragmatic (HD) palsy.

Results: Total 24 h fentanyl consumption was significantly higher in Group B (558 ± 112 mcg) compared to Group A (296 ± 88 μg). Block onset was slower in Group B than Group A. There was no difference in intra-operative fentanyl consumption. Postoperative VAS scores were significantly higher in Group B compared to Group A, at 6 h and thereafter. Duration of motor block was significantly shorter in Group B (6.25 ± 1.25 h) compared to Group A. HD palsy was seen in all the cases in both the groups.

Conclusion: Single shot nerve stimulator guided interscalene block with 10 ml of 0.5% ropivacaine was inferior to 20 mL of 0.5% ropivacaine with respect to postoperative analgesic efficacy.